Art of refining



vv. s. GULLETTE 2,132,159

ART OF REFINING @cih 4, 1938.

Filed May s, 1535 #NM www4/M MX@ Patented Oct. 4, 1938 UNl'ree stars Aer or REFINING Willis S. Gullette, Highland, Ind., assigner to Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application May 8, 1935, Serial No. 20,309

2 Claims.

This invention relates toimprovements in perations combining a fractionating operation and a vapor phase refining operation in which the vapor mixture from the fractionating operation 5 is subjected, While still predominantly in the vapor phase, to -rening treatment. The invention relates more particularly to improvements in the control of the fractionating operation in such combined operations. The invention includes apparatus for carrying out the process as Well as the process.

The invention has been found to be of special value and application in connection with operations in which complex hydrocarbon vapor mixtures, produced for example from petroleum stocks, are subjected to fractionation accurately to separate higher boiling constituents from a vapor mixture condensing to form a distillate product of the desired boiling range and in which this vapor mixture, before condensation, is subjected to refining treatment in vapor phase. Operations embodying this general scheme of 0peration have long been known and practiced. The so-called Gray processv and the so-called Lachman process for example, both refining operations applied to hydrocarbon mixtures in vapor phase, have been applied to the vapor mixture from an immediately preceding fractionating operation. In such operations as hitherto conducted, however, diii'iculties arising with respect to control of the fractionating operation have involved some compromise with respect to either the eiciency of the combined operation, the accuracy of the fractionation as reflected in the final product or both.

For example, the fractionating operation is sometimes controlled by returning to the fractionating operation as a refluxing medium a part of the final product condensed following the re- 40 lining operation, the total vapor mixture from the fractionating operation being subjected to the refining operation. Using this scheme of control, the lag through the refining operation so affects the characteristics of the final condensate that it is not effective accurately to control the separation between higher boiling constituents and constituents suitable as components of the vapor mixture separated in the fractionating operation. Consequent failure of accurate fractionation tends to overload the refining operation and thus to impair its efficiency, or alternatively to require the use of a refining system disproportionately large with respect to the net make of the final product. Further the vapor mixture from the refining operation is sometimes subthe refining operation or alternatively requires 10A4 the use of a fractionating system following the refining operation disproportionately large with respect to the net make of the final product. Again for example, the fractionating operation preceding the refining operation is sometimes 15,

controlled by returning to the fractionating operation as a refluxing medium a condensate produced by passing the total vapor mixture from the fracticnating operation from a partial Vcondenser before it reaches the refining operation. 2@

This scheme of controlis subject to a very serious disadvantage in that it dissipates part of the contained heat of the vapor mixture iiowing to the refining operation, heat which is usually necessary and almost invariably advantageous if the 25A refining operation is to be conducted efficiently and' economically.

This invention provides a process-and apparatus for controlling the fractionating operation in such operations combining a subsequent 'vapor 30 phase refining operation with the fractionating operation which, avoiding such difficulties, affords accurate and easy control of the fractionating operation Without impairing the eiciency of the refining operation and Without requiring the 35r refining operation, and any subsequent fractionating operation, to handle more than the net make of the final product. l

According to this invention, the gross vapor mixture from the fractionating operation preo ceding the refining operation is dividedv into two streams of the same composition, one of these streams is subjected to the refining operation and the vapor mixture from the refining operation is condensed, either With or without further frac- 45 tionation, to form the final product, and the other of these streams is directly condensed and the condensate so produced is returned to the fractionating operation preceding the refining operation as a. reiiuxing medium. It will be immediate- 59k.

ly apparent that the practice of this invention does not require any recirculation through the refining operation, and any subsequent fractionating operation, of any part of the nal product. The fractionating operation preceding the refin- 55 Vcontrolled by controlling the discharge of condensate from the condenser through which that part of this vapor mixture condensed to be returned as reflux condensate passes, for example to main- Y tain a.k sufficient supply of vrefluxing medium to meet the requirements, within the limits of variation for the particular operation, in a particular operation. By Yso controlling the division ofV the-gross vapor mixture, any surges'or similar disturbances within the system incident to variations in this division of the gross vapor mixture fromV the fractionating operation which might otherwise interfere with the regularity of operation are eliminated or reduced to a minimum.

The 'invention will be further described Vin connectionv vwith the accompanying drawing whichillustrates one form rof apparatus embody- Y ing "the invention and adapted Vfor carrying out the process ofthe invention.V It will be understood that the accompanying drawing is diagrammatic and conventional and somewhat in the nature of aflow chart.

In the apparatus illustrated, a vapor mixture Afrom a still'or'other source enters the fractionating tower I through vapor connection V2. Higher boiling components separated as a condensate fin' the fracti'onating tower are :discharged through liquid connection 3 Vand the fraction from which these higher boiling components are separated escapes through Vapor connection 4. Vapor connection 4 divides into twoV branches,

A 415'; one branch 4a communicatingwith condenser 5 and the other branch 4b communicating with rening tower 6. The vapor mixture from the'rening tower passes Vto condenser 'I through conn'ecti'on 8 and the condensate from condenserfl is discharged through connection 9 into receiver I0. *The final product, fractionated and Yreined, is discharged from receiver I D' through connection II. charged into accumulator I2 through liquid connection I3. Condensate` from the accumulator I2 is returned to the fractionating tower I as a reuxing medium Vthrough connection I4 by means -of pumpv I5. Connection I3 includes a valve I6 arranged t'o be operated Yby a now-controlled 'mechanism I'I to maintain an approximately j constant level in the accumulator I2, that is the Vvalve I6 is automatically controlled to open as the level in the accumulator I2 falls and to close asthis level rises. Gas separating in the receiver I'0 is discharged through connection I8. Gas separating in the accumulator I2 may be discharged either through a separate connection I9 or, by means of by-pass 20, through the connection I8 withgas from the receiver II), if the condenser 5 is designed to provide the pressure drop Condensate from condenser 5 is dis-V lower than the pressure drop through the re-V ning toWerIi and the condenser '1. Extra gas from the receiver III and from the accumulator YI2 is discharged through a common line, I8 in the apparatus illustrated, a single valve in this line, Y

2l in the apparatus illustrated, canY be used to maintain and control any pressure in the system.

In carrying out the process of the invention in the illustrated apparatus, the fractionating operation conducted in the tower YI is controlled by regulated return, through connection I4, of the condensate constituting the refluxing medium collected in accumulator I2. The return of this refluxing medium may be controlled manually or automatically, for example to maintain a predetermined temperature at the top ofthe fractionating tower I. The gross vapor mixture escaping from the fractionating operation through connection 4 is divided into twoY streams of the same composition, one passing to the refining operation conducted Yin thel tower `6 through connection 4b and the` other passing to the condenserV 5 through connection 4a. That part of this vapor mixture passing to the condenser 5 is condensed to form the reluxing medium collec-ting in accumulator I2. This part of thervapor mixture is not subjected to and does not burden the reiiningoperation conducted in jtower 6, or

may be included. The other part of the vapor mixture from the fractionating operation is subjected to the rening operation to become, when condensed, the'nal product collected in receiver f I D. No part of this nal product need be recirculated through the reiining operation in controlling the fractionating operation conductedin tower I in accordance with this invention.

I claim:

1. In an operation combining a fractionating the refining operation, condensing the otherv stream and returning the condensate so produced to the fractionating operation as a refluxing medium, and controlling the devision of the gross vapor mixture by controlling directly the dis'- charge of condensate from said condensing operation. Y Y

2l In combination, a fractionating tower, a vapor phase rening tower, a condenser and an accumulator, a Vvapor connection between the fractionating tower and therefining tower and a vapor connection, takingY a vapor mixture of the same composition as the first-mentioned vapor connection from the fractionating tower, between the fractionating tower and the condenser, a liquid connection between the condenser and the accumulator and means for returning condensate from the accumulator to the fractionating tower as a relluxingl medium,`a Yvalve in said liquid connection, and'means responsive to changes in liquid level inthe accumulator con-V 

